1. Field of the Invention
This invention relates in general to magnetic recording disk drives, and more particularly to the configuration of the air bearing surface of a slider for use in a contact start/stop magnetic disk drive.
2. Description of Related Art
Disk drives are storage devices that use a rotatable disk with concentric data tracks containing information, a head or transducer for reading and/or writing data onto various tracks, and an actuator connected to a carrier for the head moving the head to the desired track and maintaining it over the track centerline during read or write operations. There are typically a plurality of disks separated by spacer rings and stacked on a hub that is rotated by a disk drive motor. A housing supports the drive motor and head actuator and surrounds the head and disk to provide a substantially sealed environment for the head-disk interface.
In typical magnetic recording disk drives, the head carrier is an air bearing slider that rides on a bearing of air above the disk surface when the disk is rotating at its operational speed. The slider is maintained next to the disk surface by a relatively fragile suspension that connects the slider to the actuator. The slider is either biased toward the disk surface by a small spring force from the suspension, or is self-loaded to the disk surface by means of a negative pressure air bearing surface on the slider.
For contact start/stop (CSS) disk drives, the air bearing slider is in contact with the disk surface during start and stop operations when there is insufficient disk rotational speed to maintain the air bearing. To reduce wear between the disk and slider, a thin lubricant layer is placed over the surface of the disk. When a drive is turned off, the slider is typically brought to the inner radius of the disk to land on the disk surface. A dedicated textured landing area (or landing zone) is designated, typically at the inner radius of the disk surface, for the purpose of providing a landing surface for the slider and to minimize stiction.
Stiction results when the air bearing surface (ABS) of the slider has been in stationary contact with the disk for a period of time and tends to resist translational movement or xe2x80x9csticksxe2x80x9d to the disk surface. Stiction is caused by a variety of factors, including static friction and adhesion forces between the disk and slider created by the thin film of lubricant. Stiction in a disk drive can result in damage to the head or disk when the slider suddenly breaks free from the disk surface when disk rotation is initiated. In addition, because the suspension between the actuator and the slider is relatively fragile to permit the slider to fly above the disk surface, sudden rotation of the disk can also damage the suspension. As the landing zone bump height is decreased (i.e., a shallower bump height) to reduce data zone fly height, stiction is more likely to happen, which can be one of the main reasons for drive failure. Stiction can be strong enough to disable the disk spindle motor operation.
The main problem with the imparting texture to the landing zone area of the disk is that it makes the disk surface rougher and hence brings the disk surface that much closer to a flying head. As the margin between the flying height and the top most region of the texture area is reduced, thereby increasing the potential for head disk contact and hence the possibility of a head crash. Assignee""s U.S. Pat. No. 5,870,250 disclosed the use of a slider design having a single etch depth design to produce a ramp fly height profile in which the slider typically flies higher over a textured landing zone than over a data zone of the disk. The slider includes left and right rails disposed along the sides of the slider and a center crossbar connecting the rails. Extending from the center crossbar is a center rail that broadens as it reaches the trailing edge of the slider. The described slider configuration enables it to have a ramp fly height profile. However, the fly height achieved by the slider design along with other operating factors such as fly height sensitivity, altitude loss, and seek loss are not suitable for operation in disk products that require a low fly height (e.g. less that 0.50 microinches).
As the pressure to increase recording density forces lower flying heights, the balance between the need for a landing zone having a suitable bump height and the need to fly lower on the data zone is a difficult challenge. To reduce stiction, the height of the texture or bumps must be increased, but yet the fly height over the data zone is always decreasing as a result of higher density. What is needed is an improved air bearing slider design that provides a rapid fly height acceleration for clearing the textured landing zone to improve slider durability, followed by a rapid descent toward the data zone and the ability to maintain a low fly height across the data zone of the disk.
The present invention overcomes the drawbacks of the prior art by configuring a dual etch depth slider air bearing surface having novel leading end ABS, trailing ABS pad and a skewed center rail configuration, which help the slider achieve a steeper ramp fly height profile near the textured landing zone of the disk and a rapid descent toward the data zone. The air bearing slider includes a slider body on which a front pad extends from the leading edge section of the slider body to an asymmetric rear pad at the trailing edge of the slider body via a skewed center rail. The front pad supports a U-shaped leading ABS pad includes first and second sections separated by a channel. The leading ABS pad is defined near and along a leading edge (relative to a moving recording medium) and partially along the side of the slider body. An asymmetric V-shaped rear ABS pad is supported on the rear pad and defined about the longitudinal axis and proximate to a trailing edge of the slider body.